Abstract: Background: The phenotype and extent of lymphocytes infiltrating the feline pancreas are not well-described.
Objective: To characterize lymphocytes infiltrating the pancreas from shelter cats.
Animals: Forty-eight cats euthanized for population control.
Methods: Pancreata were collected within 1.5 hours of death, sectioned every 1 cm, and H&E-stained slides were prepared for histologic assessment. Sections containing lymphocytes were recut and stained with antibodies against CD3 and CD20 antigens. Distribution of T or B lymphocytes were recorded. When at least one cluster (group of at least 5 lymphocytes easily identifiable at low power) of lymphocytes was present, the percentage of T and B lymphocytes was estimated.
Results: Out of 48 cats, 13 (27%) showed clusters of lymphocytes in at least one H&E-stained section, 7 of which had cluster(s) of lymphocytes present in the recut sections stained with CD3 or CD20 antibodies. For the 39 sections with lymphocytic clusters on H&E-stained slides, 19 had clusters of T lymphocytes (median: 0%, range: 0%-50%), 16 of which were associated with clusters of B lymphocytes (median: 0%, range: 0%-75%). However, isolated T lymphocytes were commonly identified throughout the pancreatic parenchyma in many sections. T lymphocytes were most commonly periductal (85%), parenchymal (85%), or interstitial (67%); B lymphocytes were most commonly periductal (82%), interstitial (41%), or parenchymal (18%).
Conclusions: Clusters of lymphocytes were infrequently identified and were highly localized. These clusters contained both T- and B-lymphocytes in most cases and were mostly periductal. The clinical significance of these lymphocytic clusters and of isolated T lymphocytes is unknown.
